How many mAh in two cells used together

[Black Rose]

The more cells you put in series, the higher the combined voltage
(1xAA = 1.2v, 2xAA = 2.4v, etc).

Does the same apply for mAh capacity?

For simplicity, say each of those batteries are 2000 mAh batteries.
When used together, is the capacity now 4000 mAh or is it still 2000 mAh?

The reason for this question is that I am looking at a light that can take 2 RCR123A cells, so I am wondering if 2xRCR123A (750 mAh) cells is 1500 mAh or still 750 mAh versus using a 17670 cell at 1600 mAh.

 

[DM51]

Cells in series increase the voltage but not the capacity, so your 2x R123 pack will be 7.2V but still 750 mAh.

For cells in parallel it is the other way round - the voltage stays the same and the capacity increases.

 

[Marduke]

A 17670 has more energy then two RCR123's, but your light needs to be able to utilize the lower voltage. Some lights cannot, and will drop out of any sort of regulation quicker.

 

[Black Rose]

The specs for the light say it has an operating voltage of 3.7-12V or 3.6-9V (depending on which CREE is used), so it seems to cover a wide spectrum.

 

[Marduke]

That light appears to have a buck-only circuit. That means it can only be regulated on voltages above the forward voltage of the LED (around 3.7v). So when a single Li-Ion cell such as a 17670 is used, it operates in regulation for a short while. Once the voltage sags too low, the circuit stops working and the light goes into direct drive, meaning you have a dimmer, slowly declining output.

 

[Black Rose]

OK, thanks for that info. I'll go with the RCR123's then.

Oh man, I just realized what I did....I really need to get some caffeine in my system before I post on here.

For whatever reason I was thinking that since a 17670 is the size of 2 R123's and has double the capacity, it also has double the voltage (which is not true)

I always say my day is not complete until I learn something new...learning a lot today :devil: